Mr Bould's comments came as the iron ore prices slide continued down to $US91.80 per tonne over the weekend.

''When we see the numbers take a dive as they have and you don't see any clear bottom then a prudent CEO would implement a pretty straightforward plan to curtail any optimistic activity and lock down,'' he said.

''When it levels out and you understand where the bottom is and what that means in terms of costs of production, then we can re-evaluate.

''The trick for us is to protect our free cash flow and the value of our asset, so we are pretty good at belting the cost down on a short-term basis, it's not sustainable long term, but you can operate pretty cheap for a while.''

Advertisement

A $US10 movement in the iron price translates to a $US2.1 billion difference to Rio Tinto's bottom line, and $US1.2 billion for BHP Billiton, which is roughly half as exposed as its rival, according to Credit Suisse figures for the 2015 year. When applied to earnings, the Credit Suisse figures show a $US10 price movement had a 20 per cent impact on Rio and 9 per cent on BHP.

Diversified miners are ramping up iron ore production, while single-metal miners continue to add to supply, ultimately leading to oversupply and a further slump in the iron ore price.

Rio breaks even at about $US44 per tonne, while BHP comes in at $US55 per tonne. Mount Gibson's cash costs are much higher, at $US84 per tonne and Atlas's sit at $US80 per tonne. Fortescue Metals Group breaks even at around $US70 a tonne.

Despite being the first trading session since the iron ore price fell to $US91.80, shares in several Australian iron ore miners rose on Monday.

Those rises came after UBS analyst Glyn Lawcock published a note suggesting that share prices for those miners, plus BHP Billiton and Rio Tinto, were factoring in significant further falls in the iron ore price, and were duly oversold.

Speaking on Monday, Mr Lawcock pointed to better than expected manufacturing numbers out of China on Sunday as another possible explanation for the share price rises enjoyed by Atlas, Fortescue and BC Iron.

''The market has been exceptionally short on iron ore,'' he said.

Support for Grange shares was not as strong, with the stock falling 0.5¢ to 16.5¢.

Mr Bould dismissed suggestions the current price dip could be the start of the ''new normal'' for iron ore prices, saying he expected a return to $US110 per tonne before too long.

''There are lots of unusual factors impacting the market, particularly the Chinese market and we will see it start to take care of itself and even out over the next few months,'' he said.

He said recent bans on a number of iron ore mines in India was prompting some Indian buyers to target Australian producers, which could also offer support for the iron ore price.